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You should be roughly familiar with the Spread system and it's API - this document does not attempt to explain Spread in every detail. For additional information see the Spread website.

Spread has to be properly installed for this extension to work.

These procedures return an unspecified value, unless documented otherwise. Should an invocation of the Spread API fail, a composite condition of the kinds (exn spread) will be signalled, with the additional property code, containing the spread error code.

Connects to a Spread daemon. SPREAD-NAME should be of the form "<port-number>" or "<port-number>@<host-name>". PRIVATE-NAME is a string naming the connection (defaults to a randomly generated name) and should be unique on the machine running the daemon. If GROUP-MEMBERSHIP is given and not #f, then this connection will receive group-membership messages. PRIORITY is currently not used. If SPREAD-NAME is not given it defaults to a string containing the default port for spread (usually 4803).

Returns a connection object.

[procedure](sp:connection? X)

Returns #t if X is a connection object or #f otherwise.

[procedure](sp:connection-private-group CONNECTION)

Returns the private group name of this connection as assigned by the Spread daemon.

[procedure](sp:disconnect CONNECTION)

Terminates the connection. Note that a process may have multiple connections.

[procedure](sp:join CONNECTION GROUP)

Joins the group with the name GROUP (a string). If no group with this name exists, it is created.

[procedure](sp:leave CONNECTION GROUP)

Leaves the group with the name GROUP (a string). If the group does not exist, this operation is does nothing.

Sends a message to one or more groups. MESSAGE is a string containing the message to be sent, via CONNECTION and to the group or groups given in GROUP (either a string or a list of strings). The SERVICE-TYPE argument should be one of the symbols unreliable, reliable, fifo, causal, agreed or safe and specifies what kind of service is requested. MESSAGE-TYPE can be an arbitrary message code that Spread will send unchanged to all recipients.

If SELF-DISCARD is given and true, then messages sent by this connection are not sent back to the sender (the same connection).

Waits for a message from the Spread daemon on the given connection. MAX-GROUPS gives the maximal number of groups to be returned in the message object and defaults to 16. MAX-MESSAGE-LENGTH gives the maximal size of the buffer receiving the message (defaults to 1024 bytes). DESTINATION is the buffer to store the message in. If no destination is given a new buffer will be allocated. If the received message is larger than the destination buffer and MAX-MESSAGE-LENGTH is not given, then the buffer will be automatically resized and the receive-operation will be repeated. If MAX-MESSAGE-LENGTH is given and the destination is too small, an error will be signalled.

Returns a message object.

FIXME: find explanation for DROP-RECV.

[procedure](sp:message X)

Returns #t if X is a message object or #f otherwise.

[procedure](sp:message-data MESSAGE)

Returns the contents of the message: either a string (if a regular message) or a list of groups (if a regular membership message).

[procedure](sp:message-endian-mismatch? MESSAGE)

Returns #t if the endianness of the sending machine differs from that of this receiving machine.

[procedure](sp:message-sender MESSAGE)

Returns the private group name of the sending connection or the group name, if a membership message.

[procedure](sp:message-groups MESSAGE)

A list of the names of all groups receiving this message.

[procedure](sp:message-service-type MESSAGE)

A list of symbols designating the type of this message. Possible members are:

Returns #t if the message is a regular (data) message, or #f otherwise.

[procedure](sp:regular-membership-message? MESSAGE)

Returns #t if the message is a regular membership (join/leave) message, or #f otherwise.

[procedure](sp:transitional-membership-message? MESSAGE)

Returns #t if the message is a transitional membership message, or #f otherwise. (This is a message that designates a membership-change to be occurring in the future. Unfortunately this is not fully documented in the Spread manuals).

[procedure](sp:self-leave-message? MESSAGE)

Returns #t if the message is a membership (leave) message of this connection, or #f otherwise.

[procedure](sp:poll CONNECTION)

Returns #t if there is a message ready for receival (i.e. the next sp:receive will not block), or #f otherwise.

[procedure](sp:version)

Returns three values, the major- and minor version number of the used Spread library and its patch-level.

License

Copyright (c) 2004, Felix L. Winkelmann
All rights reserved.
Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following
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Redistributions of source code must retain the above copyright notice, this list of conditions and the following
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